Manufacture of hydrocarbons



UNITED STATES PATENT OFFICE MANUFACTURE OF HYDROCARBONS VladimirIpatieff and Raymond E. Schaad, Chicago, Ill., assignors to UniversalOil Products Company, Chicago, 111., a corporation of Delaware 2 Claims.

This invention relates particularly to the-manufacture of hydrocarbonssuitable for use in motor fuel blends.

Still more specifically the invention relates to the manufacture ofliquid olefinic hydrocarbons of an isomeric or branched chain structurewhich have the high antiknock characteristics of hydrocarbons of suchcondensed structure both before and after their hydrogenation to producethe corresponding paraflins.

The demands for motor fuels of continually increasing antiknock valuedue to the use of higher compression ratios in automobile and airplane lengines have been met principally by cracking the relatively heavyportions of petroleum to produce low boiling distillates of a moreunsaturated character than those produoible directly from crudepetroleums furnishing the original charging stock owing to the presenceof higher percentages of olefins, naphthenes, and aromatics. However,the production by cracking of fuels having octane numbers above acertain point which is in the neighborhood of '70 is attended withincreasing losses both as gas and heavy carbonaceous residues so that inpractice the production of fuels having higher octane numbers than 70 isa very costly proceeding. In order to conserve the values lost in thegases recourse has been had to polymerizing their ol-efinic constituentseither by thermal or catalytic processes with some success and this artis in the development stage at the present time.

The procedure most commonly followed in producing liquid hydrocarbonfractions from the gases from cracking operations has been principallyalong the line of employing the overhead 1 No Drawing. ApplicationOctober 16, 1936, 1 Serial No. 105,930

of the butenes which comprise various octenes and dodecenesrespectively.

It has been further determined that at least when employing suitablecatalysts the olefins in cuts in which they are concentrated may be moreor less selectively and successively polymerized to make individualfractions having progressively changing characteristics. For example,isobutene may be first selectively polymerized under moderately severeconditions after which the n-butenes are polymerized under more severeconditions of time, temperature, etc. and lastly the propene is causedto undergo polymerization. The polymers of the butenes are principallyoctenes and in the case of isobutene the principal product is apparentlya compound which readily hydrogenates to the well known 2,2,4-trimethylpentane which is used as a standard representing 100 octane number inthe motor testing of fuels. The octenes produced by the polymerizationof n-butenes have somewhat lower octane numbers.

Specifications for aviation fuels are particularly stringent as regardsantiknock value, saturation, and volatility, and can usually be met onlyby mixtures of isomeric paraffins boiling within the approximate rangeof from atmospheric to distillates from the cracking plant stabilizersin which the threeand four-carbon atom hydrocarbons are more or lessconcentrated. In these overhead products .commonly known as stabilizerrefluxes the percentage of so-called higher l olefinsconsisting ofpropene and the butenes may run from approximately .15 to as high as40-50% depending upon the type of cracking process from which they wereproduced. A further development has been the separation by improvedfractionation methods of the so-called butane-butene or B--B fractionswhich contain principally four carbon atom olefins and paraffins.Applying polymerization process either thermally or catalytically tostabilizer refiuxes commonly gives aliquid product having an extendedboiling range which contains polymers (principally dimers and trimers)of propene and the butenes along with some products of mixedpolymerization. In the case of the B--B fractions a large percentage ofthe polymer products are dimers and trimers 400 F., and it is thepurpose of the present invention to make possible the production ofconsiderably increased yields of isoparaffln hydrocarbons boilinggenerally lower than the iso-octanes which constitute the principalproducts resulting from the polymerization of the olefins in the BBfractions already mentioned.

In one specific embodiment the present invention comprises themanufacture of iso-heptenes by the mixed polymerization of isobutene andpropene in the presence of solid phosphoric acid catalysts.

According to the present invention mixed polymerization is brought aboutbetween two normally gaseous olefins which are not adjacent in order oftheir reactivity in polymerization reactions. As already shown the orderin which the normally gaseous olefins are polymerized as conditions ofincreasing severity are employed are isobutene, n-butenes, and propene,with a certain amount of intermediate products of mixed polymerizationwhen going from one stage to another. It has now been determined,however,

antiknock value and structure in hydrocarbons, the heptenes from theisobutene-propene polymerization are largely of isomeric structure whilethose produced from the n-butene-propene polymerization probably containhigher percentages of straight chain compounds. Owing to the difficultyof positively identifying the isomeric heptenes, no extensive effortshave been made to separate individual compounds but reliance has beenplaced principally upon the boiling range 1and octane numbers of thehydrogenated frac ions.

To obtain the isobutene and propene necessary for reaction according tothe present process, several methods may be employed. In one methodisobutene may be selectively polymerized at relatively low temperaturesof the order of normal atmospheric to 150 F. in the presence of thecatalysts to be later described and then may be separately depolymerizedat higher temperatures in the presence of the same type of catalyst. Theisobutene may also be removed by treatment with relatively weak sulfuricacid of the order of 65-75% concentration after which the ter-butylalcohol is produced by distillation of the ester and the alcohol thendehydrated by passage over such catalysts as aluminum oxide to reformisobutene. Another method of preparing isobutene consists incatalytically dehydrogenating isobutane which may be removed as aprimary product in the stabilization of gasoline since this compoundnormally boils at 13 F. while the nbutane boils at 33 F. and there is asufficient spread in the boiling points to enable a practicalseparation. The separation of isobutene from admixture with n-butenes ishardly practical since the iso compound boils at 22 F. while l-buteneboils at 24 F. and the 2-butenes boil from 34 to 365 F. As economicconditions warrant based on the increased yields of isoheptenes and theincreased octane numbers made available, any method of preparingisobutene may be employed.

The preparation of propene is a simple matter since this compound boilsat -56 F. and is readily fractionated from admixture with residualn-butenes in gaseous mixtures.

The preferred catalysts for effecting the manufacture of isoheptenescomprise the so-called solid phosphoric acid catalysts which areprepared by incorporating an equal or a major proportion by weight of anacid of phosphorus with a relatively inert and generally a siliceouscarrier to form a paste and then calcining to produce a solid cake attemperatures of the order of 300 C. followed by grinding and. sizing ofthe cake to produce solid catalyst granules. This procedure may bevaried somewhat by first extruding and cutting the paste to make smallparticles of regular form and size which are then calcined to drive offmoisture and produce as an active catalyst phosphoric acid of therequired composition. It has been determined that the best solidphosphoric acid catalysts contain an acid approaching the pyro acid incomposition as their active ingredient along with a variable amount ofsilico-phosphoric acid complexes when a highly siliceous carrier such askieselguhr has been employed in the primary mixes.

The catalysts preferred for use in the present invention arecharacterized by the fact that they are precalcined before use both tofix the composition of the acid and to form particles of a more or lesssolid character capable of withstanding the conditions of service towhich they are put. When these catalysts become coated with carbonaceousdeposits they can be regenerated by air oxidation at temperatures of theorder of 500 0. followed by contacting with superheated steam at about250-300 C. to rehydrate the acid to the most desirable composition.

The preferred conditions of operation for producing isoheptenes fromisobutene and propene with solid phosphoric acid catalysts aretemperatures of the order of ZOO-325 F. and pressures of 550 lbs. persquare inch which are maintained while passing the gas mixturedownwardly through a bed of the granular catalyst at a rate consistentwith the maximum production and antiknock quality of the isohepteneproducts. Following the polymerizing step the products are fractionatedto recover gasoline boiling range liquids while the unreacted gases areseparated and returned for further contacting with the catalyst after anexamination of the relative proportions of the isobutene and propenewhich may be altered by the addition of either compound to the mixtureas desired.

While the invention is particularly applicable to the treatment ofgaseous mixtures containing equimolecular proportions of isobutene andpropene it is also applicable to mixtures in which these reactants arepresent in nonequivalent proportions or in which they are mixed withparaffinic hydrocarbons. The principal requirement is the presence ofonly a minimum percentage of n-butenes which on the one hand would reactwith isobutene to form iso-octenes under polymerizing conditions ofmoderate severity or with the propene under more severe conditions toform heptenes of more or less normal structure.

The efficiency of the present process in common with otherpolymerizations with solid phosphoric acid catalysts, depends to adefinite extent on maintaining the composition of the phosphoric acidcatalyst in respect to its degree of hydration and for this reason bestresults in respect to life of the catalyst are obtained when a definiteamount of steam is present in admixture with the hydrocarbons undergoingreaction. The absolute amount will vary considerably with the conditionsof operation but usually are comprised within the range of 1-5%. Thispartial pressure effect serves to prevent loss of water from thecatalyst particles with the formation of the relatively inactivemetaphosphoric acid.

To show the advantages of the present invention as contrasted with othermodes of operation to recover liquid hydrocarbon fractions from normallygaseous olefins by polymerization, the following numerical data isintroduced though not with the intention of unduly limiting the properscope of the invention.

Using the solid phosphoric acid catalysts described above on stabilizerreflux and similar mixtures at 450-550 F. and 100-200 lbs. pressure,gasoline boiling range polymer products are producible which arehydrogenatable to form aviation gasolines having octane numbers from70-75.

Utilizing the 3-3 fractions and the conditions mostfavorable to theformation of isooctenes, the gasoline boiling range products may behydrogenated to produce octane fractions having -96 octane number,although there is a lack of low boiling fractions required for propervolatility in aviation fuels.

To make low boiling hydrocarbon fractions from isobutene and propene, agas mixture was prepared which had the following composition Thismixture was passed over a bed of solid phosphoric acid catalyst granulesof approximately 4-10 mesh in size which contained approximately 65% byweight of equivalent of phosphoric acid calculated as P205. To determinethe best conditions for the production of low boiling polymers havinghigh octane'number, a number of combinations of conditions were employedand the results of these experiments are indicated in the followingtable:

Mixed polymerization of isobutene and propene Average temp., F 324 257217 200 319 312 Pressure, lbs/sq. in 570 550 550 280 280 Gas charged,cu. it./hr./

pound catalyst 4. 5 3. 7 3. 9 5.5 4.6 Exit gas, cu. ft lh catalyst 0.90.9 0. 8 0. 6 0.7 Polymerization of- Propene, percent 89 60 55 62 80 69Isobutene, percent 99 98 90 93 99 99 Propane and isobutene. 95 80 77 7990 85 Ratio polymerized propene: isobutene 42:58 33:67 31:69 35:65 38:6235:65 Polymer- Gal. 1,000 cu. ft.

charged 19. 7 l7. 1 16.0 16. 2 18.1 17. 3 Fraction HEP-300 F.,

percent 68 66 72 66 64 Fraction BOO-437 F.... 28 27 21 26 37 84 Bottomsand loss 4 7 7 8 3 2 Hydrogenated IBP-300" F.

Fraction, octane number 9O 93 93 Gravity, A. P. I. at 60 F 70. 3 71. 72.3 70.0 A. S. T. M. distillation- IBP, F.-- 186 186 180 182 194 193 191196 195 196 204 199 203 226 207 239 293 226 295 99.0 99.0 98. 5 1.0 1.01.0 Percent loss 0.5 0.0 0.0 0.5 Vol. percent over at 212 F. based on:

USP-300 F. hydrogenated fraction 70 75 95 70 Total polymer 47 49 68 43Percent by weight of gas charged converted into- IBP-300 F. hydrog..- 6252 56 52 52 58 IBP-212 F. hydrog 43 39 53 50 36 37 It will be seen fromthe above table that the best results when considering the yield ofmaterial boiling below 212 F. and the 93 octane number of the materialboiling to 300 F., as well as the ratio of the propene to the isobuteneundergoing mixed polymerization that the best conditions of operationfor the particular mixture employed corresponded to from 200-220 F., apressure of 550 lbs. per square inch and a charging rate of about 4 cu.ft. per hr. per lb. of catalyst. These conditions will of course bemodified considerably when dealing with mixtures of differentcomposition and olefin concentration and when using different types ofplant equipment in respect to both absolute and relative capacities ofunits.

The nature of the present invention and it practical and commercialaspects will be evident from the foregoing specification and numericaldata respectively although neither section is intended to be undulylimiting upon the proper scope of the invention.

We claim as our invention:

1. In the polymerization of an olefinic mixture containing isobutene andpropene in the presence of solid phosphoric acid catalyst, the method ofproducing high yields of isoheptenes which comprises subjecting theolefinic mixture to the action of the solid phosphoric acid catalyst ata temperature of the order of 200 to 325 F. and under a pressure ofabout 500 to 600 lbs. per square inch whereby to effect mixedpolymerization of isobutene and propene as the primary reaction in theprocess.

2. In the polymerization of an olefinic mixture containing isobutene andpropene in the presence of solid phosphoric acid catalyst, the method ofproducing high yields of isoheptenes which comprises subjecting theolefinic mixture to the action of the solid phosphoric acid catalyst ata temperature of from about 200 to 220 F. and under a pressure ofapproximately 550 lbs. per square inch whereby to effect mixedpolymerization of isobutene and propene as the primary reaction in theprocess.

VLADIMIR IPATIEFF. RAYMOND E. SCI-IAAD.

[snAL] Patent No. 2,270,302. January 20; 1942.

. VLADIMIR IPATIEFF ET AL. It is hereby certified that error. ppears inthe printed specification of the above numbered patent requiringcorrection as follows: Page 3, first c01umn,'1ines23 to 52 lnclusive,strike out the table and insert instead the following- I Mixedpolymerization of isobutene aniii'propene' Average temp., F,

24 257 200 319 31: Pressure, lbs/sq. in 550 .510 ;1 550 250 2 Gascharged, cu. ft./hr./pound catalyst 11 8 4. 5 3.9 5. 5 4.6 Exlt gaS, cu.ft-/hr./p0und catalyst 0. 7 0. 9 0, s o, e o, 7 Polymerization of- I 1Propene, percent 89 1 62 s0 59 Isobutene, percent... 99 98 93 99 99Propene and isobutene 95 79 90 Ratio polymerized propene: isoblltene42:58 33:67 35:65 38:62 35:65 Polymer- Ga1./1,000 cu. ft. charged 19. 717.1 16. 2 18.1 17. 3 Fraction IBP300 F. percent 68 .66 7 66 60 64.Fraction 300-437" F 28 27 26 1 37 34 Bottoms and loss... 4 7 8 3 2Hydrogenated IBP-300 F.

Fraction, octane number 93 93 91 Gravity, A. P. I. at 60 F 70.3 71. b72.3 70.0 A. S. 'I. M. distillati0n- IBP, F 186 186 180 182 10 percent194 194 1 193 191 20 percent 197 196 198 50 percent 204 204 199 203 241226 207 239 324 293 226 296 98. 5 99. 0 99. 0 98. 5 1. 0 1. 0 1. 0 1'. 00. 6 0.0 0. 0 0. 5 70 75 9 6 70 47 49 68 43 62 62 56 52 62 53 IBP-212 F.hydrog 43 39 63 50 36 37 and that the said Letters the same may conformto- Signed and sealed this Patent should be read with this correctiontherein'that the record of the case in the Patent Ofiice. 17th day ofApril, A. D. 1945.

